sum_has_run = False


def sum(a, b):
    global sum_has_run

    if sum_has_run:
        print("jump out ...")
        return

    sum_has_run = True

    return a + b


print("1 {}".format(sum(100, 100)) ) # 👉️ 200

print("2 {}".format(sum(100, 100)) ) # 👉️ None
